Micropuncture techniques will be utilized in the rat to further define the segmental tubular transport of aminoglycosides and to characterize the type of inhibition of aminoglycoside transport caused by organic polycations. Basolateral membrane transport of aminoglycosides will be assessed using the isolated perfused tubule technique. In addition basolateral membrane transport of aminoglycossides will be assessed in a renal tubular cell culture line grown on collagen disc and mounted in an Ussing chamber. Cell fractionation techniques will be utilized to determine the location of the increase in renal cortical phosphatidylinositol content induced by aminoglycoside administration in the rat. Subsequently phosphatidylinositol degradation and synthesis rate will be determined. Similar studies of phosphatidylinositol metabolism will be performed in the streptozotocin-induced diabetic rat.